1. Field of the Invention
The present invention relates to a single-reel type tape cartridge in which a leader member is coupled with a leading edge of a tape. The leader member is provided for drawing out the tape to a tape drive mechanism and is coupled with a leader tape joined to a leading edge of a magnetic tape.
2. Description of the Prior Art
In order to couple the leader member with the leader tape, it is known from, for example, Japanese Patent Laid-Open Publication No. 2002-324377 that a cutout is formed at a widthwise central location of a coupling portion of the leader tape so as to define a pair of winding pieces at opposite sides of the cutout in the coupling portion and the winding pieces are wound around a pin of the leader member and turned over to the leader tape so as to be attached to the leader tape by ultrasonic welding. By rounding lateral side edges of a welding horn depressed against the winding pieces, one lateral edge of each winding piece adjacent to its distal edge and the other lateral edge of each winding piece adjacent to the pin of the leader member are subjected to welding to a more scatterable degree than other weld zones so as to prevent concentration of loads on the welded lateral edges of each winding piece such that the leader tape is prevented from being fractured at the welded lateral edges of each winding piece.
Meanwhile, fused resin may ooze out of peripheral edges of the welded winding pieces so as to be solidified. In order to prevent dropout due to drop of the solidified resin in the tape drive mechanism, it is known from, for example, Japanese Patent Laid-Open Publication No. 2001-357658 that an external shape of a welded portion is made slightly smaller than a shape of the peripheral edge of each winding piece so as to form an unwelded portion along the peripheral edge of each winding piece. A width of the unwelded portion is set at not less than 0.1 mm.
In the coupling construction of the leader member in the first prior art document referred to above, since the one lateral edge of each winding piece adjacent to its distal edge and the other lateral edge of each winding piece adjacent to the pin of the leader member are subjected to welding to a more scatterable degree than other weld zones, loads concentrated on the welded lateral edges can be scattered widely. However, from a microscopic viewpoint, as welding is performed more scatteredly, load is more likely to be concentrated on welded spots, so that the welded spots readily undergo separation and breakage and thus, it is impossible to avoid gradual drop of welding strength of the welded spots. Since a droplike space for winding the winding pieces around the pin increases by an amount of separation of the welded spots, the pin becomes loose in the coupling portion of the leader tape disadvantageously.
Meanwhile, in the coupling construction of the leader member in the second prior art document referred to above, since the unwelded portion is formed along the peripheral edge of each winding piece, ooze of the fused resin can be prevented. However, since the width of the unwelded portion is small, it is necessary to accurately position a press face of the welding horn relative to the winding pieces and thus, thereby resulting in such an inconvenience as time-consuming and troublesome welding operation.